Hi Naser,
Enter your document with FB01 and go to "Document -> Simulate General ledger" . From there you can click on "Expert Mode" button and analyze your document splitting
Check sap notes: 1085921
IMG: Financial Accounting (New) -> General Ledger Accounting (new) -> Business Transactions -> Document splitting
-> Classify G/L accounts for document splitting
-> Classify Document types for document splitting
-> Extended Document Splitting -> Define Document Spliting Rule
Kind Regards